Recently it becomes possible to exchange electronic mail or data and utilize the Internet from a wireless communication device in an office, on a street corner or in a public transportation, accompanying diversification of wireless communication devices.
It is premise that such wireless communication utilizes an infrastructure like a mobile telephone network or a local area network (LAN).
On the other hand, an ad hoc network becomes paid attention. This network temporarily establishes a network for wireless communication devices existed in the neighborhood to make them communicate together without using such infrastructure.
The ad hoc network is able to make wireless communication devices communicate together by connecting multiple stages of some wireless communication devices even if one wireless communication device can not directly communicate an arbitrary other communication device.
Hence, the network needs a process of establishing a route among wireless communication devices, which makes a decision of transferring data from one wireless communication device to other wireless communication device as a communication partner via an appropriate route.
As a communication method using the conventional ad hoc network, the non-patent document 1 discloses the ad hoc on demand distance vector method (hereinafter simply referred to as “AODV method”). This method finds a hopping route as the shortest distance to a communication partner by searching a route when a communication request is occurred in a communication device that does not hold information of a route to a destination.
In the AODV method, a communication device starts searching a route if a communication device does not an existed effective route when it transmits a data packet to other communication device as a communication partner. Then, the communication device broadcasts a route request message including the sequence number of itself, the sequence number of other communication device as a communication partner and an identifier for searching a route.
Other wireless communication device adjacently existed establishes a reverse route for the communication device that directly transmitted a route request message which the device had received if it has not sufficiently new information of a route to the other wireless communication device as a communication partner. Then, the other wireless communication device broadcasts a further route request message. But, it does not broadcast a route request message that has been already received.
The other wireless communication device as a communication partner or a wireless communication device having sufficient new information of a route to a destination wireless communication device, sends a route response message in which the sequence number of a destination wireless communication device is stored, to the wireless communication device which sent forward the route request message via unicast.
The wireless communication device which received the route request message updates route information which it has by itself based on information within the route request message and sends forward the route request message to the wireless communication device which produced the route request message via the reverse route in case when the sequence number of a communication partner is updated or numbers of hopping to a communication partner is small though the sequence number is the same.
When the request response message reaches the wireless communication device which produced the route request message, the route to the wireless communication device as a communication partner is established.
This sequential process records information of wireless communication devices into each of relay wireless communication devices. This information of wireless communication devices becomes a next hopping for sending a data packet to a destination wireless communication device. Each of relay wireless communication devices relays a data packet based on the route information from the wireless communication device as a sender to the wireless communication device as a communication partner.
In the AODV method, a route is searched only at the time when route information is needed for communication, bringing an advantage of reducing a network load due to control signals such as a route request message and a processing load burdened to a wireless communication device. Further, this method has other advantage in that an overhead for route information is not reduced since there is no need of mounting the route information to a packet header, keeping a constant length of a packet header even if the numbers of relay wireless communication devices to a communication partner are increased.
Otherwise, the patent document 1 discloses a method of designating a power every hopping. In this method, a wireless communication device regularly sends route information held by itself to other devices within an ad hoc network and records the update route information based on other route information acquired from other wireless communication devices. When performing communication, the device stores the information of a route to a destination wireless communication device, and sends it to relay wireless communication devices with transmission power information for them.
In the method of designating a power every hopping, a device makes a decision about whether a communication data property is to emphasize a transmission time delay or a frequency utilization rate, and stores the result of the decision into a packet header. The device calculates a route based on the information obtained from a routing table held by itself depending on the transmission data property. As the result of the calculation, the device stores identifiers for all other wireless communication devices relaying a data packet to be transmitted and transmission power information for each of wireless communication devices into a route information field within the packet header and sends them to a next hopping wireless communication device.
When each of relaying wireless communication devices receives the data packet of which a communication partner is designated by the original wireless communication device itself, it picks up a sending forward route from the route information stored in the route information field within the data packet and a transmission power along the sending forward route. Then, it sets the picked route information field to be a route information field of the data packet as being transmitted. Further, it sets a communication partner for sending the data packet to be a next wireless communication device along the picked route.
Then, the relaying communication device adds an operation of sending the data packet from the original wireless communication device itself into a sending forward history about the received data packet, stores it into a sending forward history field in the data packet to be transmitted and copies a data portion from the received data packet. Finally, it transmits the data packet by the transmission power which is designated via the received route information regarding the data packet.
The method of designating a power every hopping has an advantage of selecting an appropriate route in response to each of verities of telecommunication data.    Patent Document 1: Japanese issued patent No. 3585790    Non Patent Document 1: C. Perkins, E. Royer, S. Das. “Ad hoc On-Demand Distance-Vector (AODV) Routing”. Request for Comments: 3561, Internet Engineering Task Force (IETF), July 2003.